The present invention relates to a method of and an apparatus for packaging a beverage in a container. More particularly the invention concerns the packaging of a beverage (which may be alcoholic or non-alcoholic) in a sealed container, the atmosphere of which is relieved of oxygen to alleviate deterioration of the beverage by oxidation.
The invention was primarily developed for the packaging of beer such as ale, stout or lager which is sealed in a container to provide a headspace containing nitrogen and/or carbon dioxide at a pressure greater than atmospheric. In the brewing industry it is recognized that the packaging of beer in the presence of atmospheric oxygen can rapidly cause oxidation of the beer and unacceptable deterioration of its desirable characteristics. Consequently precautions are taken to insure that the contamination of beer by oxygen is alleviated during the filling and sealing stages of the container. One well known precaution in a simple beer packaging line is to purge open topped containers (such as light metal cans) of oxygen by flushing the containers with nitrogen gas immediately prior to the container being charged with beer and sealed.
In a beverage package which we have developed and which has met with considerable commercial success, a sealed container has a primary chamber charged with beverage containing gas in solution and a smaller secondary chamber which communicates with the primary chamber by way of a restricted orifice. The secondary chamber contains gas at pressure greater than atmospheric while a headspace is provided in the primary chamber also containing gas at a pressure greater than atmospheric. Upon opening of the container, a pressure differential is created causing gas and/or liquid in the secondary chamber to be ejected by way of the restricted orifice into the beverage in the primary chamber to liberate gas from solution and develop a head or froth on the beverage in the primary chamber. The secondary chamber may be formed integrally with the container or as a hollow insert which is placed within the container. Examples of beverage packages having the aforementioned secondary chamber are disclosed in our European Patent Specification A-227,213 and our British Patent No. 1,266,351.
While the aforementioned flushing with nitrogen gas may purge the primary chamber of atmospheric oxygen, because of the restricted orifice between the primary and secondary chambers such flushing as occurs in a high speed packaging/filling line has negligible effect on the oxygen content in the atmosphere of the secondary chamber. As a consequence elaborate techniques and facilities have been developed for use in a beverage packaging line by which it may be insured that atmospheric oxygen is removed from both the primary and secondary chambers prior to the containers being charged with beverage; examples of these techniques are disclosed in our British Patent Specifications 2,218,078A, 2,218,079A and 2,217,696A.
In the aforementioned prior proposals the container, particularly its primary and secondary chambers, is subjected to a sequence of pressure changes to replace the atmospheric oxygen in the primary and secondary chambers with nitrogen gas. More particularly, the container is sealed to a vacuum source and the primary and secondary chambers initially evacuated; following evacuation of the atmosphere, nitrogen gas is introduced into the primary and secondary chambers of the container and if necessary these steps of evacuation and nitrogen gas introduction can be repeated successively to ensure that nitrogen gas is substituted for the original atmosphere in both the primary and secondary chambers. During evacuation of the container its walls may be subjected to a considerable pressure differential which, in the case of fragile or thin walled containers can cause the container to collapse or implode. Modern packaging containers for beverage are frequently of a structure which, if subjected to evacuation by a vacuum pump, would rapidly collapse at very little pressure differential between the sub-atmospheric pressure in the primary and secondary chambers of the container and atmospheric pressure outside the container--this is especially true of light alloy thin walled cans which are currently favored for the packaging of beverages. To alleviate this problem our aforementioned prior Patent Specifications propose that containers which are liable to collapse during evacuation are located in a pressure chamber by which the interior, that is the primary and secondary chambers, and the exterior of the container are subjected to substantially the same pressure variations during the evacuation and nitrogen gas introduction stages. However, the pressure chambers tend to be relatively bulky and occupy considerable space in a beverage filling line where, typically but not necessarily, there will be forty package locating stations each with a beverage filling head and pressure chamber to accommodate a conventional 500 milliliter beverage can. These stations are spaced along the circumference of a rotary table which carries each can successively through its gas exchange and beverage charging stages. For a given sized rotary table, the space occupied by the pressure chambers restricts the number of can locating stations which can be provided and therefore the rate at which the cans can be processed through the gas exchange and filling stages. Also, of course, the pressure chambers together with appropriate controls for opening and closing those chambers about the respective containers adds significantly to the overall cost of the packaging equipment.
It is an object of the present invention to provide a method of and apparatus for packaging beverage in a container and by which the aforementioned disadvantages associated with the prior proposals for containers of the kind discussed (those having primary and secondary chambers which communicate with each other by way of a restricted orifice) may be alleviated so that an atmosphere having a reduced oxygen content can be provided in a thin walled or fragile container without risking collapse or implosion of the container and without requiring the container to be located in a pressure chamber.